Effect of Cyclic 3′,5′-Adenosine Monophosphate and Theophylline on Lymphocyte Transformation

Shortly after polypeptide hormones act on target tissues, the tissues undergo a series of morphologic changes that can be related to the rearrangement of vacuolar systems. Thus thyroid-stimulating hormone induces endocytosis of thyroglobulin, parathyroid hormone induces the bulk exocytosis of lysosomal hydrolases and hydrogen ions from osteoclasts, glucagon stimulates the formation of autophagic vacuoles in liver, and melanophore-stimulating hormone induces the rearrangement of melanosomes in skin (1, 2). Since cyclic 3′, 5′-adenosine monophosphate (cA MP) has been implicated as the “second messenger” for these effects of hormones upon target tissues, it appeared possible that adenine nucleotides might regulate other functions of the vacuolar system in various cell types. Evidence suggesting that increments in the level of intracellular cAMP may inhibit granule flow and merger has been obtained by Lichtenstein and Margolis (3), who found that both theophylline and dibutyryl cyclic AMP (dcAMP) inhibited the release of histamine from leukocytes. Indeed, further experiments with peripheral blood leukocytes showed that these compounds inhibited both the antigenic release of histamine and the phagocytic release of β-glucuronidase (4).

Since redistribution of acid hydrolases follows enhanced endocytosis in cultures of human lymphocytes exposed to phytohemagglutinin (PHA) (5, 6), these findings suggested that the effects of PHA on lymphocytes might also be mediated by cyclic AMP. We have therefore studied the effect of cyclic AMP, its dibutyryl derivative and theophylline (an inhibitor of cyclic AMP degradation) (1, 2) upon the stimulation of lymphocytes.

Materials and Methods. Separation and culturing of cells. Human peripheral blood lymphocytes were obtained by methods previously described. Briefly, heparinized blood was allowed to sediment spontaneously at 37°, the supernatant plasma was removed, treated with adenosine diphosphate to aggregate platelets and the filtrate was passed through a prewarmed nylon fiber column at 37°.